Method of fastening metal members to insulation



May 22, 1945. SPENCER 2,376,397

METHOD OF FASTENING METAL MEMBERS TO INSULATION Filed Aug. 7, 1941 FIG;

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Patented May 22, 1945 METHOD OF FASTENING METAL MEMBERS '10 INSULATION John A. Spencer, Newtonville, Masa, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application August 7, 1941, Serial No. 405,828

2 Claims.

This invention relates to the fastening of metal members to insulating members, such as mica, and more particularly to such fastening as is required in radio tube structures.

Heretofore, in radio tube structures, supporting metal rods have been assembled with mica insulating spacer plates by being inserted through holes in the mica and abutments being formed on the rod on either side of the mica plate to retain the rod therein. Particularly in miniature radio tubes, the space requirements of such abutments have substantially increased the size of such tubes. Further it has been difficult to mount such rods so as to prevent them from turning with respect to the mica plate.

An object of this invention is to produce a simple and effective fastening means between a metal member and a plate of insulation such as mica.

Another object is to produce such a fastening arrangement which is small in size.

A still further object is to produce such a fastening arrangement in which the metal member is rigidly and non-rotatably secured to, the insulating plate in a simple and effective manner. Still another object is to devise a simple method of producing a fastening arrangement satisfying the above objects.

The foregoing and other objects of this invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawing, wherein:

Fig. 1 is a diagrammatic view partly in crosssection showing a metal rod about to be secured to an insulating plate, together with apparatus for said purpose; and

Fig. 2 is a cross-section through my completed fastening means.

In the drawing, an insulating plate I, preferably of mica, is adapted to have a metal rod 2 rigidly a concave surface III which is adapted to engage the upper end I of the rod 2. The electrode 8 likewise is formed of some suitable conductin material, such as copper or copper alloy. as is used in spot-welding machines.

The electrode 6 is preferably held stationary while the electrode 9 is reciprocated as described above. These two electrodes are part of a device which may be the usual spot-welding machine. Thus these electrodes are connected to opposite ends of" the secondary winding ll of a current transformer l2 having a primary winding l3 energized from terminals l4, which in turn are adapted to be connected to a suitable source of secured thereto. The metal rod 2 is provided with an upper end 3 extending beyond an. annular shoulder 4 formed adjacent one end of said rod 2.

The rod 2 is inserted into a bore 5 formed in an electrode 6. The electrode 6 is of a good conducting material, such as copper or copper alloy, such as is used in spot-welding machines. The annular shoulder 4 rests against the upper end I of the electrode 6. The insulating plate I is provided with an opening 8 through which the upper end 3 projects freely. Another electrode 3 is mounted opposite the end 3'in. a position to be reclprocated, as shown by the arrows in Fig. 1. The lower end of the electrode 9 is provided with alternating current. A switch I! may likewise be provided in series with the primary winding l3 and its action synchronized with the movement of the electrode '9, in accordance with the wellknown arrangement of such spot-welding machines.

When the switch I5 is closed and the electrode 9 is forced down against the upper end 3, a relatively high current passes through said end 3 and raises its temperature to a point at which the metal 3 softens and flows under the action of the pressure exerted by the electrode I. Due to this influence the upper end 3 is formed into a rounded head I 3, as shown in Fig. 2.

I have found that in an arrangement of this kind, the rod 2 is not only retained in place on the insulating plate I, but is securely locked thereto, preventing relative turning between these two elements. It appears that this is due to the fact that the lower edges of the head It dig into the surface of the insulating plate I, as, for example, at its edges ll. Since the annular shoulder 4 is also heated during the above treatment, the upper edges of said shoulder 4 may likewise bite into the lower surface of the insulating plate I.

It will be seen that the head I and the annular shoulder 4 occupy a very limited space, and further that the resulting structure is very rigid due to the interlocking betweenthe insulating plate I and the metal member 2.

Of course it is to be understood that this invention is not limited to the particular details as described above as many equivalent will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with resilient insulating plate, passing electrical current through the outer end or said rod to raise said end to softening temperature, and exerting sumcient pressure on said softened end to cause the metal of said end to ilow and form a head and forcing the edges of said head into the plate 5 to compress said plate.

2. The method which comprises inserting a metal rod having an abutment formed thereon through an aperture in a relatively resilient insulating plate, passing electrical current through the outer end of said rod and through said abutment to raise said end and abutment to softenin; temperature and exerting sumcient pressure on said softened end to cause the metal of said end to flow and form a, head, and exerting pressure on the edges or the head and the abutment to pinch and compress the plate therebetween. JOHN A. SPENCER. 

